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From "Daniel Templeton (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-6344) Inconsistent classpath/classloading from DistributedCache archives
Date Tue, 17 Nov 2015 22:39:11 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-6344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15009742#comment-15009742

Daniel Templeton commented on MAPREDUCE-6344:

[~pk020157], in the comment explaining what you're doing, let's leave the JIRA line out of
it.  Folks can get that from git if they want to know.  Other than that, it looks good to
me.  I haven't done any testing, however.

> Inconsistent classpath/classloading from DistributedCache archives
> ------------------------------------------------------------------
>                 Key: MAPREDUCE-6344
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-6344
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 2.5.0, 2.6.0, 2.7.0, 2.5.1, 2.5.2
>            Reporter: Preston Koprivica
>         Attachments: MAPREDUCE-6344.patch
> We recently upgraded to MRv2 on YARN and have been noticing very inconsistent classloading
between the job submission client and the tasks as they start up. 
> I've tracked the issue to this method:
> https://github.com/apache/hadoop/blob/release-2.5.0/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java#L264
> It appears that the classpath is simply "wild carded".  According the javase 7&8
docs, the order of enumeration is not specified and may differ from moment to moment [1][2].
 This is a problem for applications that rely on strict ordering, which the MRv1 DistributedCache
used to provide.
> I'm unable to track down all the things that are linked or landed into the $PWD of the
container, but assuming we can't account for all these things, a simple solution could be
to explicitly enumerate the files in DistributedCache - similar to the "non jar" case [3]
- and then add the "*" for passivity.  
> [1] http://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.htm
> [2] http://docs.oracle.com/javase/8/docs/technotes/tools/windows/classpath.html#A1100762
> [3] https://github.com/apache/hadoop/blob/release-2.5.0/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-common/src/main/java/org/apache/hadoop/mapreduce/v2/util/MRApps.java#L270

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